Optical amplifiers are contemplated for use in long-haul optical fiber transmission systems where the information which is being transmitted is in the form of an encoded beam of light which propagates through a glass fiber. To obtain error-free transmission, the intensity of the transmitted light beam must be maintained within a specific allowable range. Current methodology would employ a monitoring photodetector which is physically separate from the optical amplifier to detect and measure the power output of the optical amplifier. In operation, the monitoring detector measures the average power output of the optical amplifier. The signal from the monitoring detector, acting through a feedback circuit, is employed to adjust the amplification of the optical amplifier to maintain the average power output of the optical amplifier to be within the range desired. This adjustment of the optical amplifier is required because the power output of the optical amplifier can experience a slow change or drift during operation as a result of a gradual degradation of its operating characteristics; or as a result of a variation of the degradation of its operating characteristics; or as a result of a variation of the ambient temperature.
Currently, the power output of an optical amplifier is measured by diverting a portion of the generated optical power to an optical detector which is physically separated from the amplifier. While a separate detector is adequate, it is desirable to have a photodetector which is integrated with an optical amplifier on the same semiconductor chip. Integration of an optical amplifier with a photodetector on the same chip can result in an optical amplifier photodetector device which has reduced size, can operate with increased speed, can provide high performance and have good reliability, and may eliminate substantial costs incurred in packaging the separated devices.